Method of ascertaining the center of gravity of a vessel



J. HOBDAY.

Bstermining the Sailing Trim' of Vessels. No. 3,264. s, V Patenf'ed' Sept. 14, 1843.

y; MW MW UNITED STATES PATENT OFFICE."

Mn'rHoD or ASCERTAINING THE CENTER or GRAV TY or A VESSEL, ITS BEST SAILING TRIM UNDER *VARIOUS-DEP'IHS, &o; I 1

Specification of Letters Patent No.

3,264, dated September 14, 1843.

T all whom it may concern: of the water, that brought the vessel down Be it known that I, JOHN HoBDAY, of the from mark No. l to mark N o. 2; this drum town of Portsmouth, county of Norfolk, and I now roll forward or aft on the keel or State of Virginia, haveinvented a new and lower deckuntil I bring No. 2 to the waters' 5 useful apparatus and have discovered a edge at each end of the vessel, I then sus- 60 method whereby I can find the'best sailing pend a plumb line from the center of each trim of vessels at all the various drafts of head of the drum, then remove the drum water and ascertain and remedy any deviaand strike a line across the keelson or lower tion from such trim, which may be occadeck, from each spot given by the plumbsioned by various causes, such as press of line; and that line will be the true center of 65 sail, the consumption of provisions or water gravity or displacement at that draft of from either aft or forward the center of water.. Let this process be repeated for gravity, or displacement of water, which each corresponding mark on the head and will greatly aid the judgment, in finding stern, and you have the corresponding centhe'correctplace for stepping the masts, ter of gravity or displace1nent,"for each 70 storing the cargo, &c.; also find the true draft of the vessel. 1 center of gravity'or displacement of water; Should the centers of gravity vary, or and also a new method for constructing should there be more than one center (and models and testing the same, reference being there certainly will be, if the vessel is built had to the accompanying drawings. on any plan, heretofore laid down) it will 75 Vessels are in their easiest trim and posishow that the model is incorrect, and consetion on the water, as they sit when first quently, that, there will be no definite place launched, and" at-that draft of water; and for stepping the'masts,in consequence of will consequently sail best in that position. the different centers of displacement at the This pro-position being admitted as I believe various drafts of water; and this incorrect- 80 it must be by all, I proceed to make a mark ness will be'in proportion as there are more No. 1 on the stem and stern post, at the centers, than one. 1 waters edge. I then proceed to divide the Now to correct the imperfections in the vessel into sections by means of bulk-heads, present models of vessels, I proceed on the crosswise. In each bulk-head I place a following plan, I build a'model of large 85 valve near the keel or keelson, to let the dimensions,'say 3 or 4: feet in length, and water pass freely through; I then let in a subject. the same to the above mentioned small quantity of water, suflicient to settle process, until there shall be but one center the vessel down a few inches, and then make of gravity or displacement of water. at the a mark No. 2, atthe waters edge on the same time altering the model as may be 90 stem and stern posts as before. I then pronecessary to obtain a correct one, still receed'to No. 3 in the same manner, and retaining the given dimensions of length, peat this operation, till the vessel is at her breadth and depth. The model should be lowest draft of water and fully marked. I built of some light wood, consisting only of 40 then close the valves. pump out the water, the bottom of the vessel extending a little 96 and ascertain the weight of water that each higher, than the highest lading mark. The section contains. I now remove them, and true model being thus found, the vessel may mark the rind of the ship where the bulkbe built accordingly. heads were and also mark each section, If it is required to find the best sailing showing the weight that each section will trim of vessels, already built; I build a 100 contain, and thus show the true tonnage of model from the same draft, subject it to the the vessel, or the weight that she will carry, above mentioned process of putting in the and the proportion that should be placed in water, to find her natural position at the each section to bring her down to any two various drafts of water, which will be her corresponding marks. best sailing trim. The model being built 1 To find the center of gravity or displacefrom the same draft that the ship was built ment of water, I proceed in the following from, and on a given scale, the tonnage of manner: I provide myself with a large iron the ship will be proportional to that of the drum and put into this drum, plates of lead model, and should be marked accordingly;

I until the weight of the drum shall equal that thus finding the sailing trim of the vessel at 11 I the various drafts, without subjecting the vessel itself to the process of puttingin the I water.

The masts and spars should be so arranged as to weight and position, as not materially-to change the center of displacement, the guns and cargo, to be arranged in the same manner asfar as practicable. If

the vessel be a steamer,the same rule should be observed in putting inher cargo, machinery, '&c., viz, to'retain her best sailing trim. The same principlesshould be applied to boats of all descriptions,-whether propelled by'oars or sailsthe boat' may be kept in trim, by .changing the positions of j the oarsmen, as they may 'difier in weight.

To indicate thedepth, to which the vessel I is immersed inrwater, I have a tube, (say i one-half an inch in diameter,) vpasslng through the keel, extending. along the. stem or'jsternposts; and then horizontally,along the lower deck to a stanchion or. some con:

venientplace of observation. This tube may be made of glass,zand should be graduated,

and marked, so as to, correspond withthe numbers on the stem and ste'rnof the vessel. Water always seeks a level, hence, surface'of thewa'ter-in the'tube will be (m levelwith v that ofthe'water.inwhich the vessel isim rough weather,as well, as in a calm. H

, Having described, the manner in which a i vessel maybe put, and kept in trim, in order to indicate morerreadily, any deviation from such'trim; there should be arpendulum suspended in theicabin, of which pendulum the following is an "accurate description.

' T The instrument consists of a pendulum, suspended between two platesof brass (orother metal) and connected by studs; this pendulum is designed to vibrate longitudinally or lengthwise of the vessel. The brass plates I 1' are'represented in the accompanying drawings by letters A B C D, and the pendulum by E, which vibrates freely through the arc F F, and is suspended from the center G,

c which is also the-center of the graduated i are H H andfof the movable disk numbered from 1 to 12. I is an indexer register, mov- I ing onan arc concentric with H H, also concentric with the arc described by the pendulum, and the periphery'of the movabledisk'; lK is an appendage annexed,to

indicate if necessary lthe rolling, or. trans- 'verse motion of the ship L, L are the points' by which the instrument is sus-' I pended, 'andon which the whole instrument strumentis to be suspended in the longitudinal vertical plane, passing through the keel, known in naval architecture, as the *middle line. The particular trim or position of the vessel, which may be desirable to;preserve,'after obtainingitby the usual experiments, is indicated by the vertical l1ne vibratestransversely or crosswise. The in-\ v on the ball of the-fpendulum; the point'of the'movable index Iis'there made to coin-Y cide, with the vertical line aforesaid, and

.is secured by the screw M." Should any change occur in, the given. p'osition or trim of the vessel, it will be shown by the departure of the pendulum from the index 7 point. I bring the numbers on the movable disk, correspondingwith the numbers on the stem and lstern postsfwhich is atthev water in experiments to test the velocity of the vessel in different circumstances,

Of the many advantages of the principles hereinlaid down, it maybe mentioned thatthe.=- vessel'built,and kept in trim iii-accordance. I 7

hog as'is the case with almost alL'large with foregoing plan, will not be liable-to .Waters edge, directly ovrthe verticalzline on the ball of the pendulum-the object of," which is to register the difierent drafts of v vessels; thevessel will .la'bor' less, and consequence of dlm nlshing, undue and excessive strain on any particular partof the i I I vell, it will be much more durable.

Avessel built'and fitted out inthe manner above mentioned, will notonlv sail faster than one built 'on' any other plan,- but in I consequence of a chase or other emergency,-

it should be necessary to spread more than the usual quantity of sail, the vessel will sink forward, in which case the'pendulum. will indicate'the. vibration from the best sailing trim, and the vessel maybe trimmed accordingly, by moving some after part of thevessel.

weight to the What I claim as my mvention and desire T to secure by Letters Patent is- The application iof the above process to the construction of models,lading vessels, and finding and preserving thetrue 'or center of gravity.

described i sailingrtrim of vessels at any draft of water, also finding thev true center of displacement f V JOHN HOBDAY. 

